Insulated tank assemblies such as water heaters have long been known in the art. Such structures typically comprise an inner storage tank or vessel and an outer shell or jacket. Typically, both the inner storage tank and outer jacket are cylindrical in shape. Typically the jacket is coaxial with and radially spaced from the tank so that an annular space or void is formed therebetween. A polymer foam insulating material is commonly provided in at least a portion of this annular space to provide thermal insulation for the liquid held in the storage tank.
A particularly effective insulating material for this purpose is a polymer foam that is expanded directly in the annular space between the inner tank and jacket. Various types of epoxy and polyolefin foams have been utilized for this purpose and polyurethane foam has been found to be particularly effective.
More specifically, a polymer reactive composition is injected into the void or space between the tank and jacket and the resulting foam expands to fill the available space. The polymer foam is initially fluid and sticky. It, however, slowly expands to fill substantially all the space between the tank and jacket. As the polymerization reaction reaches its completion the polymer foam becomes stiff and stabilizes into a rigid, closed cell foam that fills the annular space surrounding the tank and forms a thermal insulation for the liquid held in the tank. The amount of liquid polymer reactant composition injected into the annular space is only sufficient to ensure that the annular space is filled with polymer foam without creating excessive over-pressure in the space.
Of course, water heater tanks incorporate a number of inlet, outlet and drain fittings. Further, a gas water heater includes a heating chamber at the bottom of the tank. Specifically, a gas burner is positioned in the heating chamber and water in the tank is heated with a flame from the burner. The tank also includes sensors for thermostatic control so that the water in the tank is maintained at a desired temperature. Many polymer foams used for insulation purposes are flammable and, accordingly, they must be maintained a safe distance from the open burner flame of the heating chamber.
Toward this end, it is presently common practice to provide a foam dam device in place in the annular space between the inner tank and outer jacket at a selected position along the height of the water heater. More specifically, the foam dam is compressed between the outer wall of the inner tank and the inner wall of the outer jacket so as to seal the space therebetween. Accordingly, the inner tank, the foam dam and the upper wall and side wall of the outer jacket form a sealed space that may be filled with the insulating polymer foam. The compressive sealing engagement of the dam between the tank and the jacket prevents the polymer foam from entering the lower portion of the annular space which includes the heating chamber and burner.
The present invention relates to a wrap for insulating the water heater tank below the foam dam and adjacent the heating chamber. The wrap not only functions to insulate the water heater tank but also controls airflow in the heating chamber by preventing undesired drafts from around the burner access door provided in the outer jacket.